1. Technical Field
The present invention relates in general to the field of interface technology. Electronic components, such as modular converters for measurement control and regulation technology, particularly isolation amplifiers, are known from interface technology. Such isolation amplifiers can be used for galvanic separation, conversion, amplification and filtering of standard, normal signals and for matching analog signals. These isolation amplifiers are galvanically separated from one another in the input, output and supply circuits. This separation prevents different sensor circuits and actuator circuits from affecting one another due to the interruption of ground loops resulting from the grounding of the different circuits.
2. Background in Prior Art
Galvanic separation is accomplished by inductive passive components which are used in power conversion. The transformer is an important passive component in electrical engineering. AC voltages can be stepped up or down with the aid of a transformer. If, as in the present example, the transformer is not used for power conversion but rather for analog information transfer, the transformer is properly called a 1:1 transformer. There is also the possibility that the transformer may be used for both power conversion and signal transfer. Both electronic components operate with the same principle of inductive components. The electronic components of isolation amplifiers, including the transformer, are generally mounted on circuit boards; the circuit board may be arranged in an insulating material housing and equipped with spiral, plug-in or spring-clip terminals. The insulating material housings can be clipped onto carrier rails according to EN 50022 and thus be mounted in switchgear cabinets, for instance. The overall space available in switchgear cabinets is limited, however. Because of this limitation there exists a development requirement to minimize the overall size of electronic components, including the insulating material housing, and to manufacture them more economically.
Isolation amplifiers that are equipped with one or more passive transformers are sufficiently known from prior art, for instance, from the product catalog “Signal converter interface 2002” TNR 5123474/04.01.02-00 and the “new product catalog 2004” TNR 5154139/04.15.04-00 of Phoenix Contact GmbH & Co. KG.
Such isolation amplifiers consist of a plurality of electronic components. One of these electronic components is the transformer that serves for galvanic separation of the information signals. If there is no path by which charge carriers can flow from one circuit into another that is immediately adjacent, the two circuits are said to be galvanically separated. Information exchange between galvanically separated circuits is possible via the transformer. The transformer consists, for instance, of an annular core of soft magnetic material, which is surrounded by at least two turns of insulated conductive wire. The difficulty is to mount the transformer quickly, economically and in a space-saving manner on the circuit board of the isolation amplifier, for instance. Mounting a transformer on a circuit board therefore sets higher requirements for mounting technology. In order to mount a transformer using SMD mounting technology (SMD=surface mounting device), in which the component to be mounted is manipulated by means of a suction pipette and mounted on the surface of a circuit board, EP 1 104 931 A2 proposes using a modified annular core that has two surface areas on its narrow exterior side that form a contact surface, these areas serving to place the annular core on a carrier board and mount it thereon. The carrier board can in turn be mounted on a circuit board. DE 38 345 90 A1 describes something similar. The disadvantage of these structural arrangements is that the overall height resulting from the circuit board, the carrier board and the transformer arranged thereon is not suitable to reduce the overall width of isolation amplifiers.
DE 203 09 843 U1 proposes using a transformer that can be processed with SMD technology; it has an annular core with arranged support feet, whereby the carrier plate is unnecessary and the annular core can be directly mounted on the circuit board. With this design, the overall height is reduced by the elimination of the carrier plate, but the essential disadvantage remains that the annular core of the transformer is arranged vertically on the circuit board and thus an excessive overall height results.
DE 42 14 789 C1 therefore takes the path of mounting the annular core of the transformer horizontally on the circuit board. The great disadvantage of this design is that the windings can be fixed only with adjustment holes on the circuit board after the annular core has been mounted, and therefore it is not suitable for SMD mounting.
DE 33 18 557 A1 proposes a structural arrangement in a horizontal implementation that is suited for use on circuit boards. Reduction of the overall height is not possible here either.
DE 196 15 921 A1 describes configuration in which a cutout for receiving an annular core is contained in the circuit board. This results in a low overall height that would be suitable for use in isolation amplifiers. The great disadvantage is that mounting the element in a flat structural form is not suitable for SMD mounting technology and thus not suitable for large-scale series production. This structural design also does not meet the higher requirements for air clearance and creepage paths of the EX standard.
The invention is therefore based on the problem of creating an inductive component or transformer for isolation amplifiers of the type mentioned above that avoids the aforementioned disadvantages of the known arrangements, and of specifying a technical solution that makes it possible to produce an economical transformer for isolation amplifiers with simple functional geometry, which has a low overall height and can be mounted on circuit boards with SMD mounting technology and nevertheless meets the high requirements for air clearance and creepage paths of the EX standard.
According to the invention, this problem is solved by the characterizing features of Claim 1. Advantageous implementations and refinements of the invention follow from the subsequent subordinate claims and the descriptions below.